Field of the Invention
The invention relates to a density meter for slurry which is transported through a pipe.
Description of Related Art
Such measurements are made for instance on a dredging vessel in order to enable monitoring of the dredging process and to make optimum use of the equipment. During dredging gravel, sand and/or soil are dislodged from the bottom of for instance a waterway and pumped upward with a certain amount of water into the vessel. If the density of this pumped-up slurry is too low, the vessel will be filled mainly with water instead of with gravel, sand and soil.
Gravel, sand and/or soil are also transported in a slurry in the same way in for instance the mining industry, where it is likewise desirable for the purpose of monitoring the process to be able to make a density measurement of the slurry.
Known in the prior art are density meters for slurry which make use of radioactive radiation. The radioactive radiation here passes through the pipe with the slurry and the transmitted radiation is received at a sensor with which an indication of the density of the slurry can be obtained.
The drawback of such a density meter is that because of the use of radioactive radiation strict requirements are set in respect of operative personnel and for handling of the density meter. In addition, legislation requires that personnel have to be highly trained and that the transport of such a density meter has to comply with strict requirements. Such a density meter is moreover slow in determining the density of the slurry, thereby resulting in slow control of the dredging process.
EP07220841 describes a density meter wherein a pipe part is suspended freely between a feed pipe and a discharge pipe. Arranged over this pipe part is a portal which rests on the feed pipe and the discharge pipe. Further provided between this portal and the pipe part is a weighing cell which measures the weight of the pipe part.
In a static application the weight of the slurry in the pipe part can be measured with such a density meter and, combined with the volume of the pipe part, the density can be calculated.
As soon as this density meter is used on a vessel which rolls and pitches because of waves, the weight measurement of the pipe part will no longer be representative. Owing to for instance an up and downward movement of the pipe part the measured weight will come out higher or lower than the actual weight.
According to this publication such variations in the measured weight can be filtered out, but this will make the determination of the density of the slurry slower because measurements have to be taken over a longer period, whereby the dredging process can be controlled less quickly.
It is an object of the invention to reduce or even obviate the above stated drawbacks of the prior art.